There are certain industries which utilize extremely large quanties of lubricating oil, and the oil is usually discarded as waste after removal from an engine. The railway industry is one particular example of an industry using vast quantities of lubricating oil. Heretofore, there has been no cost-effective way of cleaning the used oil of contaminants such that the cleaned oil could be used again. Either the quality of the cleaned oil has not been sufficient for re-use in the same environment or the process of obtaining good quality oil has not been cost-effective.